Here's some pics of the piston head. Looks like charcoal. The inside of the cylinder seems mostly smooth, with a bit of rough ash like stuff on one side, seems more like ash from the piston residue. Also I shot video of the piston going up and down. It seems to be normal there. I still hear that new "click click cllck click" sound when trying to pedal start the engine. It used to do more of a "whooomp whooomp whooomp whoomp" turnover sound when starting.
YouTube - Black Piston